How does pad printing work?
Please see our excellent Introduction to Pad Printing, available on the web (or call customer service to request a copy).
Is pad printing easy, like making a photocopy?
According to our customers, pad printing is more difficult than photocopying and slightly easier than screen printing. It incorporates some old-world principles, as well as many new technological improvements that make it more of a science now than the old idea of it being an “art”. The successful pad printing machine operator will be a bit of a technician at heart that follows procedures and recipes carefully.
How do I determine if pad printing is the best way to mark my product?
As with any other technology, you must weigh its benefits and limitations against your project’s requirements to determine if you have the right match. We at Printex are always available to discuss your application with you in a plain English no-nonsense fashion.
If we have recommended pad printing to you, rest assured this is the best way (and possibly the only way) to mark your product effectively.
How do I select the right Printex machine for my application?
The primary criteria for selecting equipment are: image size, overall part size and geometry, the print position(s) per part, the number of colors per image and the number of parts per minute (or day) required. With any application, there is likely to be more than one equipment model which will accomplish the task. For most first-time pad printers, choosing the right machine is a daunting task. We at Printex routinely evaluate current and possible future applications for our customers and provide a written quotation for the recommended equipment.
Could I run my pad printer as fast as I want?
Cycle times vary widely, with a handful of interdependent factors. Most machine manufacturers (Printex included) quote top machine speed in their literature and specifications. Actual printing rates will depend as follows:
Pad printing inks dry quickly, but not instantly. Even inks that are designed to print “wet”, need a short gel time before being transferred in order to obtain acceptable results. This time window will vary with climatic conditions, ink type, plate depth, coverage, etc. The time could be as little as one second to as much as 8 seconds or more. Typically, it is 3-4 seconds without forced acceleration, such as air flow or heat.
Being a soft, three-dimensional shape, large pads may tend to vibrate at higher machine speeds. Vibration during ink pickup or transfer will yield unacceptable print results, so the machine must be slowed to allow the pads to remain steady. Additionally, pads that compress over a large print area will offer some resistance to machine movements, slowing the cycle further.
Operator and/or Auxiliary Operations.
Just how quickly can an operator load and unload your parts without fumbling? Must the operator stop periodically to move trays of parts, open boxes, or perform some other necessary function? What about upstream or downstream operations with which you must synchronize your pad printing process?
These are some of the elements that will actually determine in real time the speed at which you could run the machine.
Can pad printing machines print with other fluids besides ink?
Yes. In addition to cosmetic ink markings, pad printing has been used to apply conductive materials, lubricants, solder paste, wax, adhesive coatings, biomedical chemicals and more. The pad printer does not care what media it is transferring, as long as it meets a few basic criteria:
- The viscosity is similar to pad printing inks.
- The material is cohesive (does not bead up or lose its shape when lifted out of the plate).
- The material is reasonably homogenous (does not separate or precipitate).
- The material transfers onto the pad, rather than stick to the printing plate.
- The material sticks better to the target object (substrate) than to the printing pad.
- The material does not corrode the printing plate, attack the pad or machine parts.
We do not intend to make this sound easy. Printing of specialty fluids requires much testing and validation, but most times can be done.
Is pad printing good for applying serial numbers or date/lot codes?
Possibly – it depends upon the frequency at which the variable information changes. Serial numbers typically change with each individual part. Since pad printing is a printing plate-based process, this would require a new printing plate to be made for each part, or a re-adjustment of pad and part position which is impractical. Date codes and lot numbers may change after several hundred or several thousand parts and therefore may be feasible with pad printing, using relatively inexpensive photopolymer plates. One must weigh the cost of a printing plate and the down-time required to change the plate in the machine when considering this method.
Could I pad print very large images or objects, such as a 10
Possibly, but you are advised to explore other methods of marking or labeling for those items. Printex has produced pad printing machines large enough to print the control panels on barbecue grills and an 8.5″x11″ sheet with 100% coverage. Due to the nature of pad printing, these machines and the printing pads they utilize are necessarily very large and expensive. They apply hundreds of pounds of pressure to the part during printing. On the other hand, screen printing can be used to easily print poster-sized flat items with relative ease, and it is (by comparison to pad printing) a simple matter to apply a label to the side of a 55-gallon drum. As you may have gathered, pad printing is most efficient for smaller items and images.
Can pad printing reproduce photographic images?
Yes, in both black-and-white and full color. The pre-press preparation is a little different than what is required for standard spot printing. Photo-quality pad printing is among the most challenging of pad printing applications, particularly when attempting a high-resolution reproduction, but the results can be quite impressive.
Could I pad print parts while they are moving on a conveyor?
No. Standard pad printing requires that the part be stationary and secured during the ink transfer.
When pad printing multi-color images, does the ink have to dry between colors?
No. Pad printing inks are designed to be fast drying, and their drying speed is enhanced by the thin ink film layer therefore, “wet-on-wet” multi-color pad printing is possible. In practical use, best results are usually achieved with moderate cycle times. Occasionally the use of air flow across the pads or printed parts to accelerate the evaporation (flashing) of solvents from the printed ink is necessary.
Could I mount my Printex sealed inking pad printer sideways or upside down?
Generally no. Sealed Inking Pad Printers are designed to operate upright. The Sealed Ink Cup works on the principle of gravity. Gravity pulls the ink down into the artwork etching on the plate. However, Printex offers the RP-machine series and potential modifications of the same as a solution for vertical and upside-down printing.
Could I incorporate pad printing on a machine that performs other work as well?
Yes, as long as the basic requirements of pad printing are met. Printex provides solutions to mate with existing automation, and can design and manufacture custom systems which incorporate pad printing with pre- and post-print secondary operations. If you have a need for this service, please fill out and send our electronic quote request form, and we will contact you to discuss the detail.
Pad Printing Machines
Do I have to buy supplies from my machine vendor?
Inks: certainly the quality and performance of inks for a particular application can vary from brand to brand, but as a general rule, pad printing ink is pad printing ink. Quality, performance and price are important issues, but so are availability, support and service. Printex will gladly help you evaluate your ink needs and recommend the best product for the job, even if we do not carry it.
Plates: Photopolymer plates are easily cut to any size and supplied processed or unprocessed. Printex strives to provide superior service for your plate needs, we carry the best materials directly from the best manufacturers in the world.
Pads: much like inks, a pad is a pad, though once again quality and performance can vary. The main issue with pads, is the method by which they are mounted to the machine.
This can vary by manufacturer. Printex pads are as cross-compatible as possible in this respect.
Doctor Blades, Sealed Ink Cups and Miscellaneous: doctor blades usually boil down to thickness and width, the material comes in strips and can be cut also to length.
Printex open-well machines use standard strips of doctor blade material, we have these available in-stock in several thicknesses, finishes and widths which can be cut to any size.
Printex sealed ink cups are only compatible with Printex sealed ink cup machines.
How long do printing pads last?
Do pads yield consistent results throughout their lifetime?
What is the correct way to clean a printing pad?
What is the significance of a pad's durometer?
What is the correct way to store a printing pad?
How do I choose between photopolymer plates and steel plates?
In earlier times, alcohol plates represented the better products, now this is no longer the case. At this point, Printex G2-73 water developing photopolymer plate material is superior to other materials carried by Printex or in the marketplace. Plus, there are some alcohol-based inks which will dissolve alcohol-based plates. In this case, the advantage of water-based plates becomes even more obvious.
Could I make my own plates?
I make my own polymer plates. How do I know if they are right?
What do I use to clean a plate?
What is the difference between open ink well and sealed inking machines?
Open ink well systems (older technology) use a trough (ink well) for the ink supply, located behind the printing plate. A flood bar pushes a pool of ink over the plate, and a doctor blade removes the ink from the plate surface, leaving ink on the etched artwork area ready for the pad to pick up. Advantages are: typically smaller plate size relative to the image area. Disadvantages are: the ink supply is exposed to the air and must be frequently adjusted due to thinner evaporation, fume emissions are much higher than with sealed inking systems, open inking systems are not as clean–the inking system must be completely cleaned at the end of each production day and plate life is much shorter due to the doctor blade abrasion.
Do I have to completely fill my Printex sealed ink cup with ink?
When the cup comes to rest for several seconds, the ink settles down again. If your machine is running quickly (most machines are), the ink may never fully recover from each “wave” as regions of the engraved image will always be in the dry zone. As you probably know, if the engraved image does not get completely flooded with ink, you will not get repeatable good print results.
Could I use a smaller ink cup than the one that came with my Printex machine?
What is the best way to clean my Printex sealed ink cup?
Step 2: After a few minutes of draining, place the cup into a container filled with Printex D-Solv (or other suitable cleaner) to soak for a few minutes.
After that time, the ink should be emulsified enough for it to be cleaned off easily with a bristle brush while the ink cup is still immersed in D-Solv.
Step 3: After you’ve brushed out all the emulsified ink, and made sure that there is no ink left, take the ink cup out of the container of D-Solv, and rinse it off in warm water. Use forced air to dry the ink cup.
Are pad printing inks available in any color I want?
How do I determine what type of ink to use?
What about the environmental impact of pad printing inks?
The advent of sealed inking systems (as featured in Printex machines) has greatly reduced VOC emissions on the pad printing press.